Self-regulating system for transmission of solids in a fluid medium

ABSTRACT

A DEVICE FOR AUTOMATICALLY REGULATING THE SOLIDS TO LIQUID RATIO IN A DREDGING SYSTEM AND THE LIKE, UTILIZING PRESSURE SENSORS TO DETECT PRESSURE VARIATIONS CAUSED BY CLOGGING OR MASS RATIO CHANGES IN THE SYSTEM. THE PRESSURE SENSORS IN TURN CONTROL A VALVE OR VALVES WHICH MATER CLEAR FLUID TO THE INTAKE OF THE DREDGING SYSTEM, IN AN AMOUNT TO UNPLUG THE INTAKE AND/OR LOWER THE SOLIDS TO LIQUID RATIO TO A SAFE LEVEL.

N v- 3. 1971 J. R. HICKEY 3,621,593

$BLF-HEGULATING SYSTEM FOR TRANSMISSION OF SOLIDS IN A FLUID MEDIUM Original Filed Oct. 16, 1967 2 Sheets-Sheet l Fig. 5-

INVENTOR. JAMES I2. H 1c KEY 68 ATTO R Nov. 23, 1971 J. R. HICKEY 3,621,593

SELF-REGULATING SYSTEM FOR TRANSMISSION OF SOLIDS IN A FLUID MEDIUM Original Filed Oct. 16, 1967 2 Sheets-Shoot B Illl/f771 I 5 4 INVENTOR.

JAMEs E. HiCKEY ATTORNEY United States Patent O 3,621,593 SELF-REGULATING SYSTEM FOR TRANSMISSION OF SOLIDS IN A FLUID MEDIUM James R. Hickey, 3324 Carpenter Road, Titusville, Fla. 32780 Continuation of application Ser. No. 675,386, Oct. 16, 1967. This application Jan. 13, 1970, Ser. No. 1,989 Int. Cl. E02f 3/88 US. C]. 37-57 11 Claims ABSTRACT OF THE DISCLOSURE A device for automatically regulating the solids to liquid ratio in a dredging system and the like, utilizing pressure sensors to detect pressure variations caused by clogging or mass ratio changes in the system. The pressure sensors in turn control a valve or valves which meter clear fluid to the intake of the dredging system, in an amount to unplug the intake and/or lower the solids to liquid ratio to a safe level.

This application is a continuation of application Ser. No.- 675,386 filed Oct. 16, 1967, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to hydraulic dredging systems and the like wherein solids are transported by a liquid carrier.

In one type of hydraulic dredging system, a large centrifugal pump sucks a suspension of solids in water through an intake conduit and discharges the suspension into an outlet conduit leading to a fill area. Whenever the solids to liquid ratio in such systems exceeds a generally predetermined value, the solids agglomerate into abutting relationship and bridge across the conduit, particularly at bends in the conduit, to plug off the flow. In conventional dredging systems of this type, an operator watches a pressure gauge at the pump and adjusts the depth of the flexible intake conduit to maintain a generally constant suction pressure in the intake conduit. One difliculty of such a system is that an operator must maintain a full time watch to assure that the lines do not become plugged, and another difliculty is that many operators do not respond fast enough to prevent plugs from occurring when the system is operating close to the maximum solids to liquid ratio of which the system is capable.

An object of the present invention is the provision of a new and improved automatic system for handling solid-liquid suspensions which will substantially completely eliminate the settling out of the solids to form a plug in the system.

Another object of the present invention is the provision of a new and improved dredging system wherein the intake nozzle is automatically positioned to provide a proper solids to liquid intake ratio for preventing settling out of the solids to form plugs in the system.

'-.Another object of the present invention is the provision of a new and improved dredging system having an intake nozzle and controls therefore which substantially eliminates plugs from occurring anywhere in the system, including the nozzle.

SUMMARY OF THE INVENTION The present invention provides an improved dredging system and the like having means for removing solids from theentrance to its suction conduit and/or means for controlling the solids to liquid ratio of material flowing through its conduits. Upon sensing either a plugged entrance to the suction conduit or too high a solid to liquid ratio, the system automatically undertakes measures to either unplug the entrance to the suction conduit or to decrease the solids to liquid ratio in the system, or both. A pressure sensor is provided in either the pump suction conduit or the pump discharge conduit, and the signal therefrom is used to actuate means for unplugging the entrance to the suction conduit. Where the unplugging means is a jet of high pressure liquid, it may also be used to regulate the solids to liquid ratio of the materials flowing through the system. The system preferably includes pressure sensors in both the suction and discharge conduits and electronic means for summing the deviation from ambient pressure in both the suction and discharge conduits. The combined signal is then used to control the introduction of diluent fluid into the system either at the entrance to the suction line or at a location downstream therefrom. By using both sensors, conditions which may give rise to the development of a plug anywhere in the system are sensed, and the solids to liquid ratio is decreased to help prevent the plug from occurring. The diluent can be a pressure stream directed at the entrance to the suction conduit to both unseat a plug therein and provide a dilution of the aggregate'liquid material being pumped through the system, or in other instances may be a separate stream introduced downstream of the entrance. When a plug occurs at the entrance to the suction conduit, a large decrease in suction pressure occurs and the fluid flow velocity throughout the system is reduced. If the drop in velocity of material passing through the system is allowed to continue, additional settling out of the aggregate in the remainder of the system will occur. By opening an auxiliary inlet to introduce diluent to the system, the velocity of the material passing through the system is maintained to sweep the aggregate out of the system. Simultaneously therewith, there preferably is directed a stream of pressure fluid at the entrance to the suction line to remove the block should it have occurred at this location. The invention also provides a new and improved draft tube for a dredging system capable of operating in the manner above described.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of a dredging system embodying the present invention;

FIG. 2 is a plan view of the dredging system shown in FIG. 1;

FIG. 3 is an enlarged sectional view of the draft tube shown in FIG. 1; and

FIG. 4 is an enlarged sectional view of another embodiment of the draft tube.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The dredging system shown in FIG. 1 generally comprises a floating platform or barge 2 having a dredge boom 4 the upper end of which is pivotally connected to the front end of the barge for swinging vertical movement. A drive motor 6, be it electrical or an internal combustion engine, is mounted on the barge 2 to drive a dredge pump 8 through a suitable driving connection 10. A rotary cutter head 12 is mounted at the bottom end of the dredge boom 4 and is rotatably driven by the motor 6 through the driving connection 14. The dredge boom 4 is adapted to be raised and lowered by a cable 16 that is connected to a winch 18 also driven by the motor 6. The dirt that is excavated by the rotary cutter 12 is brought by its action to the vicinity of a suction nozzle 20 where it is caught in the flow of water which enters the suction nozzle 20. The nozzle 20 is connected to a suction conduit 22 the other end of which is connected to the inlet of the pump 8. The discharge of the pump 8- is connected to a discharge conduit 24 which extends to the fill area where the water and aggregate is dumped and the solids allowed to settle out. During operation, it sometimes happens that high concentrations of large aggregate bridge over the inlet of the suction nozzle to form a plug which stops all flow through the dredging suction and discharge conduits. When this occurs, the solids in the conduits tend to settle out and they tend to form additional plugs in the dredging conduits. The dredging system shown in the drawings includes means in the nozzle 20 which when actuated, will unplug aggregate bridging over its intake opening. This means may include reciprocating plungers, but is preferably streams of pressure fluid that are suitably directed at the intake opening, and which will, in additon to unplugging the opening, provide a flow of diluent fluid for reducing the solids-liqiud ratio of the material entering the suction conduit 22. The inlet unplugging means must be operated quickly to prevent settling out of the solids in the suction and discharge conduits, and in the preferred embodiment shown in the drawings, is actuated by sensing the downstream pressure in the suction conduit 22 or discharge conduit 24 or both. -A plug in the suction inlet will cause a drop in pressure in the suction conduit and a drop in pressure in the discharge conduit. One or the other or both of these changes produces a signal that is amplified to actuate the unplugging means in the nozzle 20. In the embodiment shown in the drawings, a transducer 26 senses the deviation from ambient pressure in the suction conduit 22, and the discharge transducer 28 senses an increase from ambient pressure in the discharge conduit 24. Electrical signals from these transducers are communicated to amplifier control circuitry 30 which in turn actuates a control valve 32 in a high pressure auxiliary diluent conduit 34 connected to the nozzle 20. Water under high pressure is supplied to control valve 32 by a high pressure pump 36 driven by the motor 6. The pump 36 takes suction from generally clear surface water through its intake conduit 38.

The high pressure diluent from the pump 36 is both used to unplug the intake to the nozzle 20 and provide reduced solids in the fluid entering the suction conduit. The valve 32 can be controlled by either of the sensors 26 or 28, but preferably by the intake sensor 26. In some instances, however, it is preferable to, in addition, provide a second diluent flow to the suction conduit downstream from the inlet to the nozzle 20. The second supply of diluent need not be a high pressure fluid, but can be generally clear water that is sucked into the suction conduit by the dredge pump 8 itself. As shown in the drawing, a secondary auxiliary conduit 42 is provided which receives generally clear water from a control valve 44 and suction screen 46. The control valve 44 is actuated by the control circuitry 30 Whenever the high pressure control valve 32 is actuated so that the flow of material through the suction and discharge conduit is not interrupted even though the inlet to the suction nozzle 20 becomes plugged. In addition to being operated when the high pressure valve 32 is operated, the secondary diluent valve 44 is preferably modulated by variations in a control signal that are the sum of the deviations in pressure from ambient presure in both the suction line and the discharge line. As the solids to liquid ratio increases in the conduits, the pressure drop therethrough increases; and by summing the total pressure drop in the suction and discharge conduits, a control signal is obtained that is a function of the amount of solids being pumped. The low pressure control valve 44 is controlled in the system shown in the drawing by the control circuitry 30 to open the valve 44 as the total pressure drop increases to thereby generally maintain the solids to liquid ratio at a safe level. The valve 44 is opened wide whenever the suction pressure drops below a predetermined level. This arrangement avoids an interruption in flow when the system is 4 pumping material having a low solids ratio and the inlet suddenly becomes plugged.

The preferred intake nozzle 20 is shown in FIG. 3. The nozzle '20 includes a draft tube 48 having a screen 50 which forms the intake opening and which is centered over the inlet to the draft tube 48. The screen 50 is frusto conically shaped, having a fiat plate 52 in line with the end of the draft tube 48 and a grid made of bars 54 forming the conical portion of the screen. The bars 54 extend radially outwardly of the draft tube 48. The space or openings between the bars 54 provide the openings through which the solids and liquid enter the draft tube 48. Any plugging thereof is removed by jets of high pressure water issuing from cleaning nozzles 56. The jets 56 receive high pressure water from an annular chamber 58 which surrounds the draft tube 48 and which is supplied with high pressure water by the high pressure auxiliary diluent conduit 34. A secondary diluent stream enters the draft tube 48 downstream from the screen 50 through secondary diluent inlets 60 that in turn are supplied with low pressure diluent from an annular chamber 62 positioned rearwardly of the annular chamber 58 from the screen 50. The secondary diluent chamber 62 is in turn supplied with liquid from the secondary diluent conduit 42.

The barge 2 may be positioned in any suitable manner and as shown in the drawing is provided with left and right spuds 64 suitable affixed to the rear of the barge. The spuds are alternately driven into the bottom to allow the barge to pivot with respect thereto. The boom 4 is caused to swing in an arc across the bottom by the force exerted by left and right towing cables 66 that are attached to left and right anchors 68 respectively. The left and right towing cables 66 are in turn pulled by left and right winches 70 that are affixed to the front of the barge. By operating the winches so that one plays out cable while the other shortens cable, the boom 4 is caused to swing in an arc across the bottom being dredged.

The embodiment of draft tube shown in FIG. 4 corresponds generally to that shown in FIG. 3. Those portions of FIG. 4 which correspond to similar portions of the embodiment of FIG. 3 are designated by a like reference numeral characterized further in that a suffix a is affixed thereto. The embodiment of FIG. 4 diflers principally from that of FIG. 3 in that the positions of the high pressure chamber 58a and low pressure chamber 62:: are generally interchanged and spaced apart. The region between the high pressure chamber 62a and 58a accommodates a plurality of annular cylinders 72 each of which contains a piston 74. Each piston 74 actuates a reciprocating piston rod 76 which projects forwardly through the low pressure chamber 62a opposite an opening between bars 54a of the screen 50a. The region on top of the pistons 74, i.e. the surface of the piston opposite its rod 76, is communicated to high pressure chamber 58a. When high pressure fluid is communicated to the high pressure diluent conduit 34a, it is also communicated to the top surface of the pistons 74 to drive the pistons forwardly towards the screen. This forces the piston rods 76 forwardly through the openings between the bars 54a to remove any debris lodged there between. The embodiment of FIG. 4 also includes a plurality of high pressure nozzles 78 which extend from the high pressure diluent chamber 58a to the region of the screens 50a to direct streams of high velocity fluid at the entrance to the screen to facilitate removal of debris. The piston rods 76 and the nozzles 78 are simultaneously actuated inasmuch as they both receive high pressure fluid from the conduit 34a.

While the invention has been described in considerable detail, I do not wish to be limited to the particular embodiments shown and described, and it is my intention to cover hereby all novel adaptations, modifications, and arrangements thereof which come within the practice of those skilled in the art to which the invention relates.

I claim:

1. A dredging system comprising: a dredge pump, a suction conduit leading to said pump, said suction conduit having an inlet opening through which a stream of water and solids to be dredged pass, a mechanically driven cutter spaced from said inlet opening for producing the subdivided solids of said stream, a grid surrounding said inlet opening through which the solids from said cutter must pass and limiting the size of said solids entering said inlet opening below the size of said inlet opening, a discharge conduit communicating with the discharge of said pump, means for producing a solids removal force out through said grid and a control valve for regulating a flow of diluent water into said stream intermediate said cutter and pump, a control means generating a first signal that is a function of the solids to liquid ratio of material being pumped through said system and generating a second signal when a plug is sensed, said means for producing a solids removal force being actuated by said second signal and said control valve being modulated by said second signal to maintain the solids to liquid ratio in said system generally constant.

2. The system of claim 1 wherein said solids removal force is a high pressure jet aimed out through said grid.

3. The system of claim 1 wherein said flow of diluent water is a nonpressurized stream introduced downstream of said inlet opening.

4. The system of claim 3 wherein the solids removal force is a high pressure jet aimed out of said grid.

5. A dredging system comprising: a dredge pump, a suction conduit leading to said pump, said suction conduit having an inlet opening through which a stream of water and the solids to be dredged pass, a mechanically driven cutter spaced from said inlet opening for producing the subdivided solids of said stream, a grid surrounding said inlet opening through which the solids from said cutter must pass and limiting the size of said solids entering said inlet opening below the size of said inlet opening, a discharge conduit communicating with the discharge of said pump, means for injecting a jet of high pressure water into the region between said grid and cutter to dilute the solids to water ratio of the stream entering the dredge, means producing a control signal that is proportional to the solids to liquid ratio of the stream passing through the dredge, and means for regulating said jet of high pressure water responsive to said control signal.

6. The system of claim 5 wherein said jet of high pressure water is aimed out through said grid.

7. The system of claim 6 wherein said suction conduit also has an entrance for an auxiliary flow of low pressure low solids content water adjacent said inlet opening and controlled by said control signal to provide an additional dredge control action.

8. The system of claim 7 wherein said grid is frustoconically shaped, a first auxiliary chamber rearwardly of said grid for confining Water under pressure, a nozzle directing pressure from said first auxiliary chamber forwardly at said opening to provide said jet, a second auxiliary chamber rearwardly of said first auxiliary chamber, and means communicating said second auxiliary chamber to said suction conduit downstream of said grid for introducing said auxiliary flow of Water into said system.

9. A method of operating a dredge having a cutter for producing a supply of loosened solids to be dredged, a

suction conduit having a submerged inlet for conveying a stream of water and solids from the cutter to a dredge pump, and a discharge conduit for conveying the stream of water and solids from the dredge pump to a remote location, said method comprising: operating the cutter at a generally constant speed that is not varied to compensate for varying operating conditions, screening the stream of water and solids entering the submerged inlet to limit the size of solids which can enter the suction conduit, providing a first control signal that is a function of the solids to liquid ratio of the stream passing through the dredge and a second signal when a plug is sensed in said inlet, actuating a positive screen unplugging action in response to the second signal and modulating a flow of diluent water into the stream of Water and solids in response to said first signal to reduce the ratio of solids to water to a desired generally constant ratio.

10. The method of claim 9 wherein the positive screen unplugging action is achieved by a high pressure jet which projects outwardly of the suction inlet against normal flow to the suction conduit.

11. A method of operating a dredge having a cutter for producing a supply of loosened solids to be dredged, a suction conduit having a submerged inlet for conveying a stream of water and solids from the cutter to a dredge pump, and a discharge conduit for conveying the stream of water and solids from the dredge pump to a remote location, said method comprising: operating the cutter at a generally constant speed that is not varied to compensate for varying operating conditions, providing a control signal that is a function of the solids to liquid ratio of the stream passing through the dredge, and regulating a jet of pressurized diluent water into the region between said cutter and the submerged inlet responsive to said control signal to maintain the ratio of the solids to liquid passing through the dredge generally constant.

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